import java.sql.*; 
public class Example11_2 {
	   public static void main(String args[]) {
		         Connection con;
			       Statement sql; 
			             ResultSet rs;
				           con = GetDBConnection.connectDB("students","root","");
					         if(con == null ) return;
						       try { 
							                 sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
											                                     ResultSet.CONCUR_READ_ONLY);
									           rs = sql.executeQuery("SELECT * FROM mess ");
										             rs.last();
											               int max = rs.getRow();
												                 System.out.println("表共有"+max+"条记录,随机抽取2条记录：");
														           int [] a =GetRandomNumber.getRandomNumber(max,2);//得到1-max之间2个不同随机数
															             for(int i:a){
																	                  rs.absolute(i);//油标移动到第i行
																			               String number = rs.getString(1);
																				                    String name = rs.getString(2);
																						                 Date date = rs.getDate(3);
																								              float h = rs.getFloat(4);
																									                   System.out.printf("%s\t",number);
																											                System.out.printf("%s\t",name);
																													             System.out.printf("%s\t",date); 
																														                  System.out.printf("%.2f\n",h);
																																            }
																               con.close();
																	             }
						             catch(SQLException e) { 
								              System.out.println(e);
									            }
							       }
}
